Second, trying to configure IIS through an installer built with WIX. The docs explain more or less clearly how to set up the custom actions, so I did that using the codes below, ran the installer, and...nothing.
Description="My Web Server"
I ran across this Strange Blog entry detailing more or less how to do the same thing, but a comment in the post also mentioned the bit I hadn't seen before: Link in the provided object file sca.wixlib to set up all the custom action scheduling the way you need it. Thanks to that commenter, the Strange Blog author, and the author of Nano CPP Unit for their help!